Complementary metal-oxide semiconductor (CMOS) sensors are generally used in charged-coupled devices (CCDs). The CMOS sensor is typically fabricated by using integrated circuit (IC) technology and includes a plurality of pixels and logic circuits. The pixel includes a light-sensitive element to convert photons into electrons. The electrons are converted into an electric signal by using the logic circuits.
Because of the course of the IC evolution, functional density (defined as the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. A scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. But, such scaling down has increased the complexity of processing and manufacturing ICs.